Osteogenic and chondrogenic proteins are able to induce the proliferation and differentiation of progenitor cells into functional bone, cartilage, tendon, and/or ligamentous tissue. These proteins, referred to herein as “osteogenic proteins,” “morphogenic proteins” or “morphogens,” include members of the bone morphogenetic protein (“BMP”) family identified by their ability to induce endochondral bone morphogenesis. The osteogenic proteins generally are classified in the art as a subgroup of the TGF-β superfamily of growth factors. Hogan, Genes & Development 10:1580-1594 (1996). Osteogenic proteins include the mammalian osteogenic protein-1 (OP-1, also known as BMP-7) and its Drosophila homolog 60 Å, osteogenic protein-2 (OP-2, also known as BMP-8), osteogenic protein-3 (OP-3), BMP-2 (also known as BMP-2A or CBMP-2A) and its Drosophila homolog DPP, BMP-3, BMP-4 (also known as BMP-2B or CBMP-2B), BMP-5, BMP-6 and its murine homolog Vgr-1, BMP-9, BMP-10, BMP-11, BMP-12, GDF-3 (also known as Vgr2), GDF-8, GDF-9, GDF-10, GDF-11, GDF-12, BMP-13, BMP-14, BMP-15, GDF-5 (also known as CDMP-1 or MP52), GDF-6 (also known as CDMP-2), GDF-7 (also known as CDMP-3), the Xenopus homolog Vgl and NODAL, UNIVIN, SCREW, ADMP, and NEURAL.
Osteogenic proteins typically include secretory peptides sharing common structural features. Processed from a precursor “pro-form,” the mature form of an osteogenic protein is a disulfided-bonded homo- or hetero-dimer, with each subunit having a carboxyl terminal active domain. This domain has approximately 97-106 amino acid residues and contains a conserved pattern of cysteine residues. See, e.g., Massague, Annu. Rev. Cell Biol. 6:597 (1990); Sampath et al., J. Biol. Chem. 265:13198 (1990).
Osteogenic proteins can stimulate the proliferation and differentiation of progenitor cells when administered with an appropriate matrix or substrate to a mammal. As a result, they can induce bone formation, including endochondral bone formation, under conditions where true replacement bone would not otherwise occur. For example, when combined with a matrix material, osteogenic proteins induce formation of new bone in large segmental bone defects, spinal fusions, and fractures.
The larynx extends from the tongue to the trachea. The trachea is a cartilaginous and membranous tube extending from the lower end of the larynx to its division into the two principal bronchi. Fibrocartilaginous tissue is found in the larynx. Cartilage forms the skeletal framework of the larynx and is interconnected by ligaments and fibrous membranes. The hyoid bone is intimately associated with the larynx, although it is usually regarded as a separate structure with a distinct function.
Abnormalities of the laryngeal skeleton influence its respiratory, defensive and phonatory functions, and can result in suffocation or loss of voice. Abnormalities can be congenital, such as cleft larynx, or acquired, such as an edema of the glottis. Excessive ossification of one or more hyaline cartilage tissues also may limit the respiratory or phonatory function. Still other abnormalities include ulceration of the larynx as a result of disease, e.g., syphilis, tuberculosis or malignancy. Abnormalities also can result from mechanical trauma to the larynx or trachea, including complications from tracheotomies. Several diseases of the human larynx, including laryngeal cancer, involve the laryngeal skeleton. Treatment of these and other conditions may involve partial or complete removal of the laryngeal skeleton or trachea (tracheotomy, laryngotomy, or laryngotracheotomy). Surgical reconstructive procedures of the larynx or trachea are complex. To date, reconstruction has relied on cartilage grafts, small intestine grafts, and cellular adhesives such as fibrinogen or cyanoacrylate to reattach torn tissue. Common complications include graft rejection and/or fibrous transformation of autografts or allografts.
Fibrocartilaginous tissue is found not only in the larynx, but also in other regions including the ear, nose, ribs, intervertebral discs and interarticular menisci. Repair and reconstruction of defects in these tissues requires regeneration of appropriate functional replacement fibrocartilage.